It's on the rear of the kayak actually. It makes the overall profile of the boat's waterline thicker closer to the bow, a shape that boat-builders refer to as "cod-headed" and which has been used to add speed to Adirondack guideboats for a hundred years.
This boat was $310 NEW. Look up Perception Acadia Scout. It's a junior model but I bought it when I weighed in at 185 lbs and it was fine.
I attached the keel using a pre-existing bolt hole that was molded into the plastic, and then stabilized it with 3 screws right into the hull- one through each of the metal straps, and one that you can't see that is countersunk up into the wood at the base of the keel extender to keep it from twisting.